Cancer is the second leading cause of human death next to coronary disease. Worldwide, millions of people die from cancer every year. In the United States alone, cancer causes the death of well over a half-million people annually, with some 1.4 million new cases diagnosed per year. While deaths from heart disease have been declining significantly, those resulting from cancer generally are on the rise and are predicted to become the leading cause of death in the developed world.
Cancers are characterized by multiple oncogenic events that collectively contribute to the phenotype of advanced stage disease. With the advent of new drugs that target specific molecular abnormalities, it is important to know whether the initial oncogenic event continues to play a functional role at later stages of tumor progression and at relapse with the development of chemotherapy resistance. This question has been addressed in transgenic mice through regulated expression of the initial oncogene. In three models testing different oncogenes in different tissues, the primary oncogene was required to maintain the tumor phenotype, despite the presence of numerous additional oncogene and tumor suppressor mutations (see, e.g. L. Chin et al., Nature 400, 468 (1999); D. W. Felsher et al., Mol. Cell 4, 199 (1999); and C. S. Huettner et al., Nature Genet. 24, 57 (2000)). Recent clinical trials of the Abelson tyrosine kinase (Abl) inhibitor STI-571 in chronic myeloid leukemia (CML) allow this question to be addressed directly in human cancer (see, e.g. B. J. Druker et al., N. Engl. J. Med. 344, 1038 (2001); and B. J. Druker et al., N. Engl. J. Med. 344, 1031 (2001)).
CML is a pluripotent hematopoietic stem cell disorder characterized by the Philadelphia (Ph) chromosome translocation (see, e.g. C. L. Sawyers, N. Engl. J. Med. 340, 1330 (1999); and S. Faderl et al., N. Engl. J. Med. 341, 164 (1999)). The resulting BCR ABL fusion gene encodes a cytoplasmic protein with constitutive tyrosine kinase activity (see, e.g. J. B. Konopka et al., Proc. Natl. Acad. Sci. U.S.A. 82, 1810 (1985) and NCBI Accession NP_067585). Numerous experimental models have established that BCR ABL is an oncogene and is sufficient to produce CML-like disease in mice (see, e.g. G. Q. Daley et al., Science 247, 824 (1990); and N. Heisterkamp et al., Nature 344, 251 (1990)). CML progresses through distinct clinical stages. The earliest stage, termed chronic phase, is characterized by expansion of terminally differentiated neutrophils. Over several years the disease progresses to an acute phase termed blast crisis, characterized by maturation arrest with excessive numbers of undifferentiated myeloid or lymphoid progenitor cells. The BCR-ABL oncogene is expressed at all stages, but blast crisis is characterized by multiple additional genetic and molecular changes.
A series of inhibitors, based on the 2-phenylaminopyrimidine class of pharmacophores, has been identified that have exceptionally high affinity and specificity for Abl (see, e.g., Zimmerman et al., Bloorg, Med. Chem. Lett. 7, 187 (1997). The most successful of these, STI-571 (formerly referred to as Novartis test compound CGP 57148 and also known as Gleevec and imatinib), has been successfully tested in clinical trail a therapeutic agent for CML. STI-571 is a 2-phenylamino pyrimidine that targets the ATP-binding site of the kinase domain of ABL (see, e.g. B. J. Druker et al., Nature Med. 2, 561 (1996)). In phase I clinical trials, STI-571 induced remissions in patients in chronic phase as well as blast crisis (see, e.g. B. J. Druker et al., N. Engl. J. Med. 344, 1038 (2001); and B. J. Druker et al., N. Engl. J. Med. 344, 1031 (2001)). While responses in chronic phase have been durable, remissions observed in blast crisis patients have usually lasted only 2-6 months, despite continued drug treatment (see, e.g. B. J. Druker et al., N. Engl. J. Med. 344, 1038 (2001)).
In view of the relapse observed in patients treated with STI-571 there is a need for an understanding of the mechanisms associated with STI-571 resistance in CML and related cancers as well as diagnostic and therapeutic procedures and compositions tailored to address this phenomena. The invention provided herein satisfies this need.